I'm skeptical too. I mainly asked because of what Freddd said, but maybe he'll clarify his theory. I don't want to misstate it. Just because you both used the term "limiting factor" doesn't mean you're talking about the same thing.
Ten years ago on May 21st, 2003 at 6:05 pm MDT I knew my life was changed. Adding MeCbl made a HUGE difference. At the same time it was my first intro to donut hole folate deficiency and an obviously induced hypokalemia. However the hypokalemia was mild and handled by 400mg/day of potassium. What I immediately noticed as I did my first round of balancing titrations I found out that all sorts of vitamins and minerals clearly worked better when I titrated them. After I added AdoCbl another group of items suddenly made a difference, another limiting factor. Then, some years later when I got up to CNS penetrating doses, I had the same experience with adding AdoCbl and AdoCbl at those doses made a few other items work very differently, like SAM-e. I needed LESS SAM-e after getting the CNS MeCbl higher. Metafolin made MORE difference. After AdoCbl, more Zinc made more difference.
Going back into the 50-70s the warning about vitamins, was about the risks of induced deficiencies when not taking all the vitamins and minerals. Until MeCbl my thought on that was "I wish they worked so well as to make any observable difference"., Without the MeCbl and AdoCbl, hundreds of pathways were not working right. They were severely limited by lack of MeCbl and NOTHING I could try made any noticeable difference at all except 100 tablets a day of desiccated liver. That validated my hypothesis that what I needed, "protein mystery factor" (wrongly identified and Nobel Prize for Cyanocobalamin), NOT the CyCbl that I was taking.
Now consider the paradoxical symptoms switches of a slow exit from methyltrap. When MeCbl is low it is distributed on a triage by level effect, same as methylfolate. When b12 is low enough to be in partial methylation block the worsening symptoms are typically b12 deficiency symptoms because it breaks at the lack of sufficient b12. In Methyltrap, after MeCbl gets even lower, the methylfolate has no b12 available and is expelled from the cell which then BREAKS the process at folate. A little bit of MeCbl then returns the person to b12 deficiency symptoms which switch back to folate deficiency in a few days if more isn't taken..
Then as soon as there is some healing taking place something else goes short enough to "break" something and other symptoms become more intense, "unmasked" or "induced" or any number of ways of thinking about it.
So in this situation something broke in a way that something caused a hard drop in potassium and methylfolate and yet I also had rapid failure of at least some immune functions, epithelial problems, neurological deterioration from a previous healing state. So, as Dbkita said before "this isn't healing". But perhaps it can give us a clue as to what broke for some number of us. There are all sorts of limiting factors. However perhaps only one at a time, the FIRST break in a process is the one that gets the symptoms.